[Groups] Edit group details (PUT /groups-management/groups/{id})

[TheRealSeber]

Implement UI and remote function to allow teachers to edit the details of an existing group using PUT /groups-management/groups/{id}.

Requirements

• Add an edit button/dialog/form for group details.
• Use a remote function: PUT /groups-management/groups/{id}.
• Match existing editing UX for Tasks management.
• Integrate validation (valibot), feedback, and i18n (Paraglide).
• Ensure code supports extensible access roles.

Child of [Groups] Implement groups management for teachers (parent issue): #139 READ IT before implementing anything